The overall goal of this project is to study, by biochemical techniques, the novel proteins that are produced after infection of Escherichia coli with the T-even bacteriophages. Previous work on this project led to the discovery of a deoxyribonuclease (T4 exonuclease A) which is induced by phage infection. Mutants of T4 were also discovered that are deficient in ability to induce T4 exonuclease A and T4 endonuclease II. The objectives of this project include (a) enzyme purification of T4 exonuclease A (b) characterization of its enzymatic properties and substrate specificity (c) physiological studies on mutants deficient in T4 exonuclease A. and (d) studies directed to identification of other nucleases which may have a role in degradation of the DNA of the host after T4 phage infection.